3Phase, 120/208VAC panelboard with 2-Pole branch 50A CBs - using one pole only for 120V to loads

Status
Not open for further replies.
I

Isaiah

Senior Member
Location
Baton Rouge
Occupation
Electrical Inspector
My question is if they're using only one pole (say, Ph A) off a 2-pole branch 50A CB to get 120V - i.e. phase and neutral - will the 50A CB still adequately protect the circuit? They're using 3 #6AWG wire. This is for temporary construction power to a 'spider box' (portable power distribution box) that contains several 20A, 120VAC receptacles for small power tools, like grinders etc.
 
As Tom was hinting at the 20 amp receptacles cannot be protected by a 50 amp OCPD. Other than that it is OK to feed this box with a single 120 volt circuit from a multi-pole CB if the box has integral overcurrent protection for the 20 amp devices.
 
infinity said:
As Tom was hinting at the 20 amp receptacles cannot be protected by a 50 amp OCPD. Other than that it is OK to feed this box with a single 120 volt circuit from a multi-pole CB if the box has integral overcurrent protection for the 20 amp devices.
Click to expand...

Thanks for feedback. Yes it has internal 20A CBs


Sent from my iPhone using Tapatalk
 
So you understand, a 2 pole breaker still has individual current sensors on each pole that function independently from each other. So if EITHER of them senses more than 50A, it causes a trip. The trip unit will open both poles simultaneously, but you don't care, so long as the one you are connected to opens.
 
Jraef said:
So you understand, a 2 pole breaker still has individual current sensors on each pole that function independently from each other. So if EITHER of them senses more than 50A, it causes a trip. The trip unit will open both poles simultaneously, but you don't care, so long as the one you are connected to opens.
Click to expand...
Thanks Jraef. I did not know that.
 
Isaiah said:
Thanks Jraef. I did not know that.
Click to expand...
What else you should know is, even if you pried off the handle tie, both poles would still trip, due to an internal mechanical link.

The handle tie is there to assure simultaneous manual operation, which is why a tie is adequate for multi-wire branch circuits.
 
LarryFine said:
What else you should know is, even if you pried off the handle tie, both poles would still trip, due to an internal mechanical link.

The handle tie is there to assure simultaneous manual operation, which is why a tie is adequate for multi-wire branch circuits.
Click to expand...

Awesome. Thanks Larry.


Sent from my iPhone using Tapatalk
 
What is this spider box that has only one 50 amp hot going to it? Every spider box I have ever seen is a H-H-N-G 4 wire supply. Did someone wire it up like this because they only had 6/3 and not 6/4? Or is it some homemade contraption?
 
Todd0x1 said:
What is this spider box that has only one 50 amp hot going to it? Every spider box I have ever seen is a H-H-N-G 4 wire supply. Did someone wire it up like this because they only had 6/3 and not 6/4? Or is it some homemade contraption?
Click to expand...

Cable at the Panelboard is definitely 6/3. I assumed therefore, they’d use one pole and run 120V to the box with H, N and G. Now I’m not so sure. I’ll delve further into this one for sure.
Thanks for the observation.


Sent from my iPhone using Tapatalk
 
Isaiah said:
Cable at the Panelboard is definitely 6/3. I assumed therefore, they’d use one pole and run 120V to the box with H, N and G. Now I’m not so sure. I’ll delve further into this one for sure.
Thanks for the observation.


Sent from my iPhone using Tapatalk
Click to expand...

ooh I hope they didnt wire it H-H-N and omit the EGC
 
Todd0x1 said:
ooh I hope they didnt wire it H-H-N and omit the EGC
Click to expand...

A closer look at the cable shows Southwire 6/3 and 8/1. The plug/receptacle are rated 50A with 3 poles, 4 wires...part numbers CS6364C and CA6365C.


Sent from my iPhone using Tapatalk
 
Isaiah said:
A closer look at the cable shows Southwire 6/3 and 8/1. The plug/receptacle are rated 50A with 3 poles, 4 wires...part numbers CS6364C and CA6365C.


Sent from my iPhone using Tapatalk
Click to expand...
As in black, red, white all #6 and a green #8?

Should be able to use both poles of your two pole breaker and have twice the VA capacity out of the spider box.
 
Status
Not open for further replies.
Top